2018/2019 Mountains and Foothills Fall/Winter Thread

[BretWx]

Just... beautiful. There's not one in here that would be a bad storm. 

[Boonelight]

It is absolutely pouring snow again in Deep Gap. This pic doesn’t do it justice.

 

[Rainforrest]

36 minutes ago, BretWheatley said:

Not to be selfish, but that 20in lollipop is right over Henderson county. I'm STILL hesitant to go all in on this one. 

Southern escarpment should do well

[Tyler Penland]

Still snowing pretty good here in Vilas. Amazed this is still going tbh.

[BlueRidgeFolklore]

Jason Boyer update is still sticking to 10-20+ for the majority of mountains outside the far southwestern portion.

[BretWx]

GSP - Wow. 

We are approaching increases in the
official fcst QPF cautiously since even modest snow ratios from
these values would result in snow/sleet accumulations that might
be a once-in-a-generation event for parts of the Piedmont.

[BlueRidgeFolklore]

First, 'First Call' map I've seen.

 

[BretWx]

3 minutes ago, BlueRidgeFolklore said:

First, 'First Call' map I've seen.

 

Wild to watch this play out. 

[BretWx]

WLOS Jason said the word “historic” - get ready 

[Rainforrest]

I would like to hear hurricanetrackers thoughts on what’s about to happen. 

[HurricaneTracker]

Just now, Rainforrest said:

I would like to hear hurricanetrackers thoughts on what’s about to happen. 

Will do. Hopefully this evening after dinner time 

[strongwxnc]

I would like to hear hurricanetrackers thoughts on what’s about to happen. 

Dude you’ll get nailed!


.

[SENC]

2 hours ago, Boonelight said:

It is absolutely pouring snow again in Deep Gap. This pic doesn’t do it justice.

 

Nice! While I had muh windeers open here at the Coast today, (airing out the house).. Like night & Day

[SnoJoe]

Didn't get the 5 inches I wanted but did end up with about 4.5. And had a high today of only 22.8.

I want to say thanks to the folks that keep us updated here. I rarely venture outside of this thread mostly because I don't understand 90% of what they're talking about. Plus, the posts come so fast I can't keep up anyway. I know it's a pain sometimes to repeat yourselves for us but know that people like me appreciate it because it lets us enjoy our passion for weather too. 

[Met1985]

37 minutes ago, HurricaneTracker said:

Will do. Hopefully this evening after dinner time 

I was wondering when you would chime in. I'm packing up and trying to get the hell out of Wisconsin tonight.  Ironically its snowing up here as well. 

[Boonelight]

32 minutes ago, SENC said:

Nice! While I had muh windeers open here at the Coast today, (airing out the house).. Like night & Day

Night and day for real! No way I had the windows open here. It’s been below freezing all day.

[BretWx]

Holy hell @ the 18z FV3 snowing through hr 138... 

[strongwxnc]

Holy hell @ the 18z FV3 snowing through hr 138... 

Holy hell is right.


.

[HurricaneTracker]

Hi all.  I hear some folks have asked for my take on the current winter storm.  Happy to help and participate here when I can and when I think my posts will be informative (rather than just banter or MBY endless posts).  So here goes.  AND do note - this is for the mountains of WNC only.  Sorry other readers.

I think most, if not all, of you have the general idea that a big winter storm is on tap.  That storm system is currently entering Southern California (which is a great thing for them!).  They are in serious drought out that way and every storm system helps.  The southern position of the upper level low moving onshore in associated with a strong subtropical jet are two very common characteristics of El Niño.  So you will see some folks in the main thread refer to this as an El Niño wave.  In El Niño years, the subtropical jet (STJ) flows fast from west to east from SoCal through southern Texas and into the Gulf Coast states.  That is exactly what we have here.   By Saturday, this jet buckles tremendously as our low gets carved out, with wind speeds greater than 180 knots (almost 200 mph)!  This is very intense and only seen with the biggest storm systems in the mid-latitudes.  The southeastern states will be under the right entrance region of the jet (a proxy for upward vertical motion).

Then we have the full wave at 500mb moving in across the ArkLaTex region at 18Z Saturday.  Meanwhile, a strong northern stream wave is forecast to be located over central North Dakota.  Over time, the GFS model does not ever phase (I.e., merge) these two waves into one.  Instead, the primary wave that comes into California scoots across the Deep South and induces a surface low pressure system near Houston, TX basically first thing Saturday morning.  This low draws upon rich and deep gulf moisture (characterized by precipitable water values in excess of 1.40” - incredibly deep for December and sourced from the STJ and eastern Pacific!  Wow!  By Saturday night and into Sunday morning, this deep moisture is pointed straight at the southern Apps, much like a fire hose but with deep tropical connections.  Meanwhile, as the surface cyclone moves into southern Georgia, we have southwest winds aloft but locally we have southeast winds circulating around our low.  This in turn brings in a secondary layer of moisture at the surface, combined with deep tropical moisture aloft.  I just cannot emphasize how big a deal this tropical fire hose is.  Even in spring this would be a big deal (for severe weather/flooding reasons).

The surface low however has other things to work with.  A seasonally-strong cold cP (continental-polar) airmass, will be building into the Midwest on Friday and Saturday.  In winter, anything over 1040mb is a very cold airmass.  This high pressure is basically squeezed east as the STJ buckles and mass evacuation (I.e., air parcels being ejected from the center of the low pressure in Texas), act to strengthen the squeeze (confluence) in the Midwest.  Let’s not forget this high will be moving over some snow cover, which acts like a refrigerator.  Some models handle the intensity of such highs differently.  Regardless, all models take the high into New England and then the cold oozes southwest, hugging the entire Apps Chain all the way to western NC.  Enter the wedge.  This wedge is sourced from cold air in New England.  Wedging is reinforced (I.e., positive feedback loop) by dynamical cooling from precipitation and ageostophic adjustment due to barrier winds.  We have all those ingredients here.   Southeast winds around the low act to also serve as an “upslope” mechanism, inducing upward vertical motion and enhancing any existing synoptic-scale vertical motions.  Oof.  

Score one for the NAM here.  GFS has been very bad so far this year with wedging air masses (too warm).  It has always played catch up while the CMC and RGEM greatly (and I do mean greatly!) overdoes the cold wedge.  NAM seems to be the sweet spot (did I just type that?).  It has a 1038mb high moving into position during the day Saturday. So, the question is, how cold?  Ignoring surface temperatures for the time being, the 850mb temperatures (~5000’) stay below freezing the entire time!  The cold is REINFORCED by precipitation and 35 knot southeasterly winds above the surface.  Surface temperatures are also below freezing, as a stready wind vector from the NE funnels cool and dry cP air into the storm system, and the forecast soundings (thermal profiles) remain ALL SNOW on the GFS model.

Take a moment and examine the thermal profile I shared here for 7pm Saturday night.  Note that very deep isothermal layer (layer of equal temperature...below freezing) from the surface to 700mb.  This is a classic WNC heavy duty, paper machete, snow sounding.  And I can tell you our thermal profiles stay this way for a while.  Oof.

So, let’s review. We have 1) cold high pressure wedging down...check.  2) source of upward vertical motion (double check).  3) moisture?  Oh heck yea.  CHECK.  And this is just the southern stream wave!  The northern stream eventually comes down to reinforce the growing trough over the east coast giving us our second punch in the gut.

OK.. now here is where I lay down my personal thoughts having digested and explained it all here.  <takes off the gloves>

I want to impart a few things on you guys.  Stop looking at the snow maps.  They are assuming 10:1 ratios....and just by looking at those soundings, you can absolutely tell it won’t be 10:1 (I am thinking 7:1, based solely on experience).  You should be looking at trends in the QPF.  And you should NOT look at the QPF from the GFS - why?  Because it has been wrong by a factor of 2, and even 3, most of the fall season in western North Carolina!  (Not saying it could be right elsewhere, but for now, WNC has been missed badly by the GFS).  Here the Euro and NAM models have performed very well in this department.  And you gotta think...BIG source of tropical moisture.  Plus Atlantic moisture.  Plus vertical motion.  Plus jet dynamics.  When the dynamics are there the moisture will find a way.  We are not lacking dynamics.  Euro was around 3.00” of liquid equivalent.  NAM isn’t out this far yet.  GFS was 1.40” (multiply by a factor of 2 and you get 2.80”).  Dang!  That’s a LOT of liquid.  Thermal profiles support snow, and maybe some sleet far southern escarpment as the warm nose tries to invade (briefly).

10:1 ratio gives you 28-30” of snow.  Bwa ha ha ha.  I can’t do it.  Just can’t do it.  What did GSP say, “generational” event?  You bet.

7:1 ratio still gives 15-18” of cement snow.  Oof.  Who in their right mind feels good about issuing a forecast like that around here?  It’s unheard of.  Can it happen?  It could.  Would I go with these values at day 4 (looking at you WYFF)....no.  Why not?  Because the atmosphere is always in motion.  Things flow like saltwater taffy being pulled from two ends.

And we still have time to watch this.  BUT BUT BUT...we have been watching this since Saturday, Dec 1.  It is equally mind-boggling to me to think that the large scale pattern and such has been so incredibly consistent for so long!  The Weather Prediction Center now has the mountains 70-90% chance of a major winter storm at DAY 4!  Wow. 

The Euro has a 96% chance of 6” or more from this system.  The GEFS mean is creeping up (on QPF...more snow, less sleet/ZR as the wedge is better reflected).

Oh and start time?  BANK ON EARLIER rather than later.  I have seen this time and time again.  These systems break out precipitation along the warm fronts and into the cold dome earlier than most systems.  GFS might have this right.  Another trend to watch next 2-3 days.

Alright, enough rambling.  Hope it’s helpful.  TL;DR - get ready.  Prepare now for a big snow event with potential for prolonged power outages. This is as big a deal since December 2009.  if you live anywhere in the cold air damming favored areas of WNC (sorry Franklin), this storm has your number.

 

 

 

[wncsnow]

4 minutes ago, HurricaneTracker said:

Hi all.  I hear some folks have asked for my take on the current winter storm.  Happy to help and participate here when I can and when I think my posts will be informative (rather than just banter or MBY endless posts).  So here goes.  AND do note - this is for the mountains of WNC only.  Sorry other readers.

I think most, if not all, of you have the general idea that a big winter storm is on tap.  That storm system is currently entering Southern California (which is a great thing for them!).  They are in serious drought out that way and every storm system helps.  The southern position of the upper level low moving onshore in associated with a strong subtropical jet are two very common characteristics of El Niño.  So you will see some folks in the main thread refer to this as an El Niño wave.  In El Niño years, the subtropical jet (STJ) flows fast from west to east from SoCal through southern Texas and into the Gulf Coast states.  That is exactly what we have here.   By Saturday, this jet buckles tremendously as our low gets carved out, with wind speeds greater than 180 knots (almost 200 mph)!  This is very intense and only seen with the biggest storm systems in the mid-latitudes.  The southeastern states will be under the right entrance region of the jet (a proxy for upward vertical motion).

Then we have the full wave at 500mb moving in across the ArkLaTex region at 18Z Saturday.  Meanwhile, a strong northern stream wave is forecast to be located over central North Dakota.  Over time, the GFS model does not ever phase (I.e., merge) these two waves into one.  Instead, the primary wave that comes into California scoots across the Deep South and induces a surface low pressure system near Houston, TX basically first thing Saturday morning.  This low draws upon rich and deep gulf moisture (characterized by precipitable water values in excess of 1.40” - incredibly deep for December and sourced from the STJ and eastern Pacific!  Wow!  By Saturday night and into Sunday morning, this deep moisture is pointed straight at the southern Apps, much like a fire hose but with deep tropical connections.  Meanwhile, as the surface cyclone moves into southern Georgia, we have southwest winds aloft but locally we have southeast winds circulating around our low.  This in turn brings in a secondary layer of moisture at the surface, combined with deep tropical moisture aloft.  I just cannot emphasize how big a deal this tropical fire hose is.  Even in spring this would be a big deal (for severe weather/flooding reasons).

The surface low however has other things to work with.  A seasonally-strong cold cP (continental-polar) airmass, will be building into the Midwest on Friday and Saturday.  In winter, anything over 1040mb is a very cold airmass.  This high pressure is basically squeezed east as the STJ buckles and mass evacuation (I.e., air parcels being ejected from the center of the low pressure in Texas), act to strengthen the squeeze (confluence) in the Midwest.  Let’s not forget this high will be moving over some snow cover, which acts like a refrigerator.  Some models handle the intensity of such highs differently.  Regardless, all models take the high into New England and then the cold oozes southwest, hugging the entire Apps Chain all the way to western NC.  Enter the wedge.  This wedge is sourced from cold air in New England.  Wedging is reinforced (I.e., positive feedback loop) by dynamical cooling from precipitation and ageostophic adjustment due to barrier winds.  We have all those ingredients here.   Southeast winds around the low act to also serve as an “upslope” mechanism, inducing upward vertical motion and enhancing any existing synoptic-scale vertical motions.  Oof.  

Score one for the NAM here.  GFS has been very bad so far this year with wedging air masses (too warm).  It has always played catch up while the CMC and RGEM greatly (and I do mean greatly!) overdoes the cold wedge.  NAM seems to be the sweet spot (did I just type that?).  It has a 1038mb high moving into position during the day Saturday. So, the question is, how cold?  Ignoring surface temperatures for the time being, the 850mb temperatures (~5000’) stay below freezing the entire time!  The cold is REINFORCED by precipitation and 35 knot southeasterly winds above the surface.  Surface temperatures are also below freezing, as a stready wind vector from the NE funnels cool and dry cP air into the storm system, and the forecast soundings (thermal profiles) remain ALL SNOW on the GFS model.

Take a moment and examine the thermal profile I shared here for 7pm Saturday night.  Note that very deep isothermal layer (layer of equal temperature...below freezing) from the surface to 700mb.  This is a classic WNC heavy duty, paper machete, snow sounding.  And I can tell you our thermal profiles stay this way for a while.  Oof.

So, let’s review. We have 1) cold high pressure wedging down...check.  2) source of upward vertical motion (double check).  3) moisture?  Oh heck yea.  CHECK.  And this is just the southern stream wave!  The northern stream eventually comes down to reinforce the growing trough over the east coast giving us our second punch in the gut.

OK.. now here is where I lay down my personal thoughts having digested and explained it all here.  <takes off the gloves>

I want to impart a few things on you guys.  Stop looking at the snow maps.  They are assuming 10:1 ratios....and just by looking at those soundings, you can absolutely tell it won’t be 10:1 (I am thinking 7:1, based solely on experience).  You should be looking at trends in the QPF.  And you should NOT look at the QPF from the GFS - why?  Because it has been wrong by a factor of 2, and even 3, most of the fall season in western North Carolina!  (Not saying it could be right elsewhere, but for now, WNC has been missed badly by the GFS).  Here the Euro and NAM models have performed very well in this department.  And you gotta think...BIG source of tropical moisture.  Plus Atlantic moisture.  Plus vertical motion.  Plus jet dynamics.  When the dynamics are there the moisture will find a way.  We are not lacking dynamics.  Euro was around 3.00” of liquid equivalent.  NAM isn’t out this far yet.  GFS was 1.40” (multiply by a factor of 2 and you get 2.80”).  Dang!  That’s a LOT of liquid.  Thermal profiles support snow, and maybe some sleet far southern escarpment as the warm nose tries to invade (briefly).

10:1 ratio gives you 28-30” of snow.  Bwa ha ha ha.  I can’t do it.  Just can’t do it.  What did GSP say, “generational” event?  You bet.

7:1 ratio still gives 15-18” of cement snow.  Oof.  Who in their right mind feels good about issuing a forecast like that around here?  It’s unheard of.  Can it happen?  It could.  Would I go with these values at day 4 (looking at you WYFF)....no.  Why not?  Because the atmosphere is always in motion.  Things flow like saltwater taffy being pulled from two ends.

And we still have time to watch this.  BUT BUT BUT...we have been watching this since Saturday, Dec 1.  It is equally mind-boggling to me to think that the large scale pattern and such has been so incredibly consistent for so long!  The Weather Prediction Center now has the mountains 70-90% chance of a major winter storm at DAY 4!  Wow. 

The Euro has a 96% chance of 6” or more from this system.  The GEFS mean is creeping up (on QPF...more snow, less sleet/ZR as the wedge is better reflected).

Oh and start time?  BANK ON EARLIER rather than later.  I have seen this time and time again.  These systems break out precipitation along the warm fronts and into the cold dome earlier than most systems.  GFS might have this right.  Another trend to watch next 2-3 days.

Alright, enough rambling.  Hope it’s helpful.  TL;DR - get ready.  Prepare now for a big snow event with potential for prolonged power outages. This is as big a deal since December 2009.  if you live anywhere in the cold air damming favored areas of WNC (sorry Franklin), this storm has your number.

 

 

 

Great post. Thanks

[BretWx]

@HurricaneTracker thank you for that. Just read most of it out loud to my family, ha! I know a lot can change, but I’m getting close to being all on board. 

[ncjoaquin]

Very nice HT. Thanks for your insight. 

[HurricaneTracker]

4 minutes ago, BretWheatley said:

@HurricaneTracker thank you for that. Just read most of it out loud to my family, ha! I know a lot can change, but I’m getting close to being all on board. 

Dude, thanks!  I am incredibly humbled that you’re willing to share my long *** write up with your family. I tried to make it light-hearted and witty.  You know, share a little fun and excitement for a “generational” snow event.  Sure do appreciate your support!

[ncjoaquin]

The GEFS  mean is 18.45 !!!  The GFS deterministic is the bottom.  Let me add the mean was 2.27 precip so HT knows I read what he said. 

[BlueRidgeFolklore]

5 minutes ago, HurricaneTracker said:

Dude, thanks!  I am incredibly humbled that you’re willing to share my long *** write up with your family. I tried to make it light-hearted and witty.  You know, share a little fun and excitement for a “generational” snow event.  Sure do appreciate your support!

HT, that was an incredible write up.

[strongwxnc]

Dude, thanks!  I am incredibly humbled that you’re willing to share my long *** write up with your family. I tried to make it light-hearted and witty.  You know, share a little fun and excitement for a “generational” snow event.  Sure do appreciate your support!

Yup. It was long...
Awesome insight man! Thanks for the time !


.

[BretWx]

13 minutes ago, ncjoaquin said:

The GEFS  mean is 18.45 !!!  The GFS deterministic is the bottom.  Let me add the mean was 2.27 precip so HT knows I read what he said. 

I’m torn between believing watching history unfold (weenie, I know) and still being extremely skeptical. Cheers! 

[jburns]

Well done, sir. Thank you.

 

[Rainforrest]

Thanks great explanation 

[BlueRidgeFolklore]

1 minute ago, BretWheatley said:

I’m torn between believing watching history unfold (weenie, I know) and still being extremely skeptical. Cheers! 

15-18".

HT said so.